The Thin-winged Owlet has a wingspan of approximately .75 inch. The sharply pointed narrow forewings are white with a slanting black median bar that connects with a black costal streak. Bands of brown and gray shading pass on either side of the white, jagged subterminal line. The dotted terminal line is black. The hindwing is gray with a small, black triangle near the anal angle. The caterpillar is elongate, brown and white with a bumpy appearance. It lacks prolegs on abdominal segments 3 and 4, and abdominal segment 5 is reduced in size and shifted rearward.